Actually in my experience, it's exactly the opposite. I listened to the advice of Petco when I got my first snake and fed in a separate enclosure. Neither of my snakes seemed to like me taking them out of the feeding box and putting them back in their own enclosures. Especially Floyd. He tagged me a few times and tried several more. After reading the forums and seeing how many people were feeding in the enclosure with no problems, I decided to try it once to see how it went. My snakes struck the rats from under their hides no problem. I haven't had a snake bite since.

I think it's a security thing as much as it is a "Don't touch me while I'm trying to digest" thing.